1. Field of the Invention
The present invention relates to a rechargeable battery, and more particularly, to a rechargeable battery that can be suitably applied for a battery module in which a plurality of such rechargeable battery cells are connected in series.
2. Description of Related Art
FIG. 11 shows a conventional battery pack made by connecting a plurality of rechargeable batteries and coupling them together as one so as to obtain a necessary power. In this battery pack, a plurality of cells 41 (41a to 41j) made of sealed alkaline rechargeable batteries as shown in FIG. 12 are arranged in a row, with the long lateral walls of the battery cases 42 adjacent each other. End plates 52 are arranged against the outside of the cells 41a and 41j at opposite ends, and the cells are coupled together as one piece with binding bands 53.
For the cells 41, as shown in FIG. 12, an electrode plate group 47, comprising positive electrode plates and negative electrode plates layered with intervening separators, thus constituting elements for electromotive force, is accommodated in a battery case 42 together with a liquid electrolyte, and the open end of the battery case 42 is closed with a lid 46 provided with a safety vent 45. From the upper end at one side of the positive electrode plates forming the electrode plate group 47, leads 49 extend upward and are connected to a positive electrode terminal 43 above them, and similarly, from the upper end of the other side of the negative electrode plates, leads 49 extend upward and are connected to an negative electrode terminal 44 above them. These positive electrode terminal 43 and negative electrode terminal 44 are then attached to the lid 46.
In FIG. 11, the positive electrode terminals 43 and negative electrode terminals 44 of coupled neighboring cells 41 are connected by connection plates 51, thereby connecting all cells 41 in series. When the battery cases 42 are coupled, ribs 48, which protrude vertically from the long lateral walls of the battery cases 42, are abutted against each other, forming coolant passages running in the vertical direction along the long lateral walls of the battery cases 42 in the space between ribs 48. The cells 41a to 41j are cooled by flowing air through these coolant passages.
With the configuration for the cells 41 of this conventional battery module, leads 49 extend from a portion at the upper end on one side of the electrodes and are connected to the electrode terminals 43 and 44, that are mounted to the lid 46, and further, the portions of the electrode terminals 43, 44 protruding above the lid 46 are connected with each other by the connection plates 51. As the connection between adjacent cells requires a complicated structure with a large number of components, costs are relatively high, and the electrical resistance at the connection is large. Moreover, since it is necessary to provide a space for the connection structure above the battery case 42, and since the connection structure is exposed to the outside, the space for installing this battery pack cannot be made compact.
Moreover, in the portions where electrode pillars of the electrode terminals 43 and 44 extend through the lid 46, O-rings for providing a seal are usually placed only on the inner side of the lid 46, and there was the danger that electrolyte may leak during the use of battery.
In view of these problems of the prior art, it is an object of the present invention to provide a battery module. comprising a plurality of rechargeable batteries, which can be constructed at low cost and in which cells are simply connected to each other. A further object of the present invention is to provide a battery module, of which installation space can be made compact, and in which there is no danger of electrolyte leakage.
To achieve the above object, the present invention provides a rechargeable battery, comprising:
a prismatic case having short lateral walls and long lateral walls;
a group of electrode plates encased in said prismatic case together with a liquid electrolyte;
a positive electrode collector plate and a negative electrode collector plate attached to the group of electrode plates at long lateral opposite ends thereof;
a connection hole formed in the short lateral walls of the prismatic case; and
a connection boss formed in said positive electrode collector plate and the negative electrode collector plate such as to fit into said connection hole.
According to the present invention, two neighboring cells are connected together via connection bosses that are formed in the collector plates of the electrode plate group. Therefore, the connection structure of two cells is simply constructed without any extra components and thus at low cost. Moreover, thanks to the compact connection structure between the cells, the space for installation of the battery module can be made compact.
A sealing material can be arranged around the connection boss for providing a seal against the outside, whereby the connection hole is sealed double from both sides and leakage of electrolyte during the use of battery can reliably be prevented.
The connection boss in the collector plates may be formed by compression molding such that the connection boss is protruded on one side of the collector plate, so that the connection boss can integrally be formed with the collector plate with high productivity and at low cost. When welding the leading ends of the abutted connection bosses together, a pair of welding electrodes having protrusions at their ends can be used, wherein the protrusions of the welding electrodes are respectively inserted into the cavities formed on the backside of the connection bosses. Thereby, pressure can be concentrated at the leading ends of the connection bosses and the welding can be performed favorably. The connection structure with small electric resistance can thus be obtained with high reliability.
Alternatively, a reinforcing member may be embedded in a cavity that is formed on the backside of said connection boss such that the reinforcing member is flush with a plate surface around said cavity. In-this case, welding of the leading ends of the connection bosses can favorably be accomplished even with welding electrodes having flat distal end surfaces. That is, even with the welding electrodes without protrusions as mentioned above, pressure can be concentrated at the welding portion, whereby the welding can be performed favorably, and the connection structure with small electric resistance can be achieved reliably. Moreover, since the welding electrodes need only be formed flat at their distal ends, they can be used longer, and the overall cost for the manufacture of the battery can be reduced.
Alternatively, the connection boss may be formed with an annular projection in an outer peripheral portion at a protruding end of the connection boss. In this case also, welding electrodes with flat distal end surfaces can be used, by which pressure is transferred and concentrated at the annular projection at the outer periphery of the leading ends of the bosses. At the same time, the annular projections of the two connection bosses that are abutted each other form an annular welding line, whereby a large welding area can be attained, and the welding is performed favorably. The connection structure with small electric resistance can thereby be achieved reliably. Moreover, welding electrodes having flat distal end surfaces can be employed even without the reinforcing members as mentioned above that are embedded in the cavities, and therefore, the overall cost for the manufacture of the battery can be reduced.
The rechargeable battery of the present invention can advantageously be applied to constitute a battery module, wherein an integral battery case is comprised of a plurality of the rechargeable batteries as described above. Upper open ends of the plurality of cell cases are integrally closed by an integral lid member. In accordance with the present invention, neighboring cells can be connected within the integral battery case, and the connection structure between the cells is not exposed to the outside. Thereby, a battery module according to the present invention is more compact and requires less installation space than conventional battery modules.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.